1. Field of the Invention
The present invention relates to a surge absorption element and a surge absorption circuit.
2. Description of the Related Art
A semiconductor device such as an IC or LSI is damaged by high-voltage static electricity or the characteristic of the semiconductor device deteriorates. Hence, a surge absorption element such as a varistor is used for the semiconductor device as static electricity countermeasure.
Further, surge absorption elements including varistors have a stray capacitance component or a stray inductance component. Hence, when a surge absorption element is applied to a circuit carrying a high-speed signal, the high-speed signal is made to deteriorate. If the stray capacitance component of a surge absorption element must be made small in order to apply the surge absorption element to a circuit carrying a high-speed signal, degradation of the leading edge characteristic and delay characteristic of the high-speed signal is unavoidable. However, when the stray capacitance component of the surge absorption element is small, the rise in the control voltage of the surge absorption element and the energy resistance must be reduced.
A surge absorption element that comprises an inductor and two varistors as surge absorption elements that alleviate the effects of the stray capacitance component is known (See Japanese Patent Application Laid Open No. 2001-60838, for example). The surge absorption element that appears in Japanese Patent Application Laid Open No. 2001-60838 comprises a parallel circuit comprising a first varistor and an inductor, a second varistor that is electrically serially connected to the parallel circuit, and an I/O electrode and grounding electrode that are connected to the two ends of the serial circuit of the second varistor and parallel circuit.
However, because, in the case of the surge absorption element appearing in Japanese Patent Application Laid Open No. 2001-60838, a bandpass filter is constituted by the stray capacitance of a first varistor, and an inductor, impedance matching is difficult to achieve over a wide bandwidth. Therefore, an adequate characteristic cannot be implemented for a high-speed signal. Further, not only is impedance matching with respect to a high-speed signal preferable but also miniaturization of the element itself is desirable.